A power controlling method in a communication system is one of radio resource management methods for efficiently using limited frequency resources, and it solves a near-far problem.
In a code division multiple access (CDMA) communication system, since a terminal uses one code channel, transmission power of the terminal is determined by a gain of a power amplifier. Accordingly, in the CDMA communication system, an open-loop power control operation for compensating a path loss caused by a distance between a base station and the terminal, and a power control operation for compensating inaccuracy of the open-loop power control operation, are performed by controlling the gain of the power amplifier. Since the terminal uses one code channel in the CDMA communication system, the gain of the power amplifier may be controlled to perform the power control operation in a cell.
Differing from the CDMA communication system, in an orthogonal frequency division multiplexing access (OFDMA) communication system, the transmission power of the terminal is set to be lower than that of the base station so that one subchannel may be used in a cell boundary area. Accordingly, since the terminal may use subchannels from a single subchannel to all subchannels, the limit of a full loading range (FLR), which is a distance in which the terminal may use all the subchannels, may be restricted. In the FLR, the power amplifier of the terminal uses a maximum gain.
Accordingly, the terminal positioned outside the FLR may not perform the open-loop power control operation for increasing the gain of the power amplifier to compensate the path loss that increases according to an increase of the distance between the base station and the terminal. In addition, since an initial ranging (IR) signal transmitted by the terminal outside of the FLR has a low strength when it is received by the base station, an initial ranging operation may not be performed.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.